A general motor is made as shown in FIG. 1 and FIG. 2 with a structure in which a motor main body 1 and an inverter 2 are respectively separated, and the motor main body 1 and the inverter 2 are connected by electrical wires so as to be electrically connected which is not shown in the drawings.
A volume knob 3 for adjusting a frequency is provided to the inverter 2, and when the frequency is adjusted by utilizing the volume knob 3, a voltage is applied to the motor main body 1 side through lead wires (not shown) within a motor terminal box 4 which are connected with electrical wires connecting the motor main body 1 and the inverter 2, so that a rotor 5 rotates at a speed corresponding to the respective voltage and frequency in accordance with a rotating principle of a normal induction motor.
In the drawings, unexplained reference numeral symbol 6 represents a rotary shaft, numeral 7 represents a stator, and numeral 8 depicts an inputting electric power connecting means.
However, as described above, since a general motor is divided respectively into the motor main body 1 and the inverter 2, a very long electrically wire is required for connecting these, and there has been a disadvantage in that not only their storing was not easy but also a disposal of electric wires was not easy. In the case of mounting the inverter 2 to the motor main body, a magnetic noise and vibration of the inverter 2 itself was generated at low rotational speed, i.e., low frequency region, and a respective separate fan for cooling the motor and inverter and fan motor for driving this had to be provided. Accordingly not only much space was required but also their constitution was complicated and much trouble arose from this arrangement.